According to the Water Research Foundation’s Residential End Uses of Water report, toilets are the single largest source of indoor water use in the average US home. On average, toilets account for nearly one-quarter of all indoor household water consumption, consuming 11,900 gallons of water per year.

Factors that influence toilet water consumption

The total amount of water a toilet uses depends on two main factors:

1. How often the toilet is flushed
2. How much water the toilet uses per flush

According to the World Toilet Organization, most people flush a toilet between 6 and 8 times per day. In homes with multiple occupants, the total number of annual flushes adds up quickly.

Toilet water usage is measured in gallons per flush (gpf). Older toilets installed before the 1990s often used between 3.5 and 7 gallons of water per flush. Modern federal standards require most new toilets to use no more than 1.6 gallons per flush, while many high-efficiency toilets use only 1.28 gallons per flush or less.

The difference in annual water use can be dramatic. Assuming 8 flushes per day, these are the annual water consumption totals for various toilet flush rates:

• A 5-gpf toilet uses more than 14,000 gallons of water per year
• A 1.6-gpf toilet uses about 4,600 gallons per year
• A 1.28-gpf toilet uses about 3,700 gallons per year

The operating costs of toilets

Toilets only consume cold water, so their water consumption only impacts your water and sewage bills. In the US, the average cost per gallon of water via water utility companies is $0.015. This seems small, but when it applies to thousands of gallons of water per year, the total cost adds up.

For example, let’s assume there are 4 people living in a home, and each person flushes a 1.6-gpf toilet 8 times per day. This equals 11,680 flushes and 18,688 gallons per year. At a rate of $0.015 per gallon, that’s over $280 per year just to flush the toilet.